Inflammation at the Tissue-Electrode Interface in a Case of Rapid Deterioration in Hearing Performance Leading to Explant After Cochlear Implantation

Abstract

Objective: The reasons for soft failure after cochlear implantation require investigation. This study proposes a method to study and characterize the tissue response to the array in a case of soft failure in a person undergoing reimplantation. Case: The woman in her 50s, with an underlying autoimmune condition, received a cochlear implant using hearing preservation technique after developing profound hearing loss more than 2 kHz with a moderate loss of less than 500 Hz over a 10-year period. The case was identified as a soft failure due to deteriorating performance, discomfort, and migration over the 10 months after implantation. Impedance telemetry, speech perception measures, and audiometric thresholds are described. At explantation there was evidence of fibrosis. Intervention(s): To use histology and immunohistochemistry to determine the cellular response of the tissue associated with the electrode array at time of explantation. Main Outcome Measure(s): Identification of the cell types, regional variations, and inflammatory marker expression in the fibrotic tissue associated with the array. Results: Neutrophils and eosinophils were identified, along with a variable pattern of collagen deposition. CD68 and CD163-positive macrophages and T cells were variably distributed through the tissue and interleukin-1 beta and vascular endothelial growth factor receptor-2 expression was identified. Conclusions: The expression profile is evidence of active inflammation in the tissue despite the time since implantation. This study is the first to characterize the tissue response to the array in a person undergoing reimplantation, and who can be followed to determine the individual response to arrays. It establishes that the investigation of explanted devices after soft-failure is feasible.

Macrophages in the cochlea; an immunological link between risk factors and progressive hearing loss

“…The inflammatory response to this is likely as has been described above and should resolve as part of a normal wound healing response. However, in some individuals there is a chronic inflammatory response, which promotes the excessive deposition of fibrotic tissue around the array, which develops long after the surgical intervention, leading in some cases to reduced performance with the device (Bas et al, 2015; Hough et al, 2021; Nadol et al, 2008, 2014).…”

A high-throughput 3D X-ray histology facility for biomedical research and preclinical applications

“…400 × 400 mm 2 , which allows imaging specimens with an effective diameter less than 40 cm. Using this system at the 3D XRH facility, a range of soft tissues have been imaged to date, including healthy and fibrotic human lung FFPE samples 2 , lymph node biopsies 29 , human pulmonary lymphatics 30 , placenta 31 , HSC-3 cell-xenografted severe combined immunodeficiency (SCID) mouse tissue 32 , bone marrow biopsies, as well as hard tissues 33 and micro-implants in situ such as cochlear implants 34 .…”